Rollability prediction system

ABSTRACT

In a railway classification yard a car&#39;&#39;s rollability is measured several times as it is traveling through the upper yard. These measurements are employed to predict the car&#39;&#39;s rollability on the bowl track. From the predicted rollability, means are provided to determine what the car&#39;&#39;s velocity should be when it leave the last retarder just prior to entering the bowl portion of the yard in order that it travel the distance required to couple to a stationary car at the proper velocity.

United States Patent 7 Wong et al. Sept. 5, 1972 [54] 'ROLLABILITYPREDICTION SYSTEM FOREIGN PATENTS OR APPLICATIONS [72] Inventors: PeterJ- g, Menlo Park; Dale 924,205 4/1963 Great Britain ..246/l82 A Ross,Sunnyvale; Kenneth W. Gardmer Menlo. Park n of Cahf- PrimaryExaminer-Gerald M. Forlenza [73] Assignee: Southern PacificTransportation Assistant Examiner 6e0rge Libman Company, San Francisco,Calif. Attorney-Lindenberg, Freilich & Wasserman [if] lllrled: N Oct.23, 1970 [57] ABSTRACT PP- 83,365 In a railway classification yard acar.s rollability is I measured several times as it is traveling throughthe [52] US. Cl. ..246/ 182 A upper d, These measurements are employedto pre- Clthe car's on the track FfQm the [58] Field of Search ..246/182A; 275/ 150.2 predicted rollability means are provided to determine whatthe cars velocity should'be when it leave the last [56] Refergnces C'tedretarder just prior to entering the bowl portion of the UNITED STATESPATENTS yard in order that it travel the distance required to 1 cou leto a stationa car at the r0 r veloci 3,054,893 9/1962 Dasburg ..246/ 182A p ry 'l ty 3,014,658 12/1961 Hermes 246/182 A 4 Claims, Drawing 22 ,264

F t \2 V L MA$TER 72? Y EETARDER COMPUTER ,3'6 Rm (DMPUTER ,so vELocn'Ycbfivirr n I58 coM 5TER R5 comm 122mm CONTROL BOWI TRACK EPEED DETECTORrmmtnszr 5 m2 sum 1 or 2 PATENTEDSEP 5 I972 sum 2 or 2 SUMMER MULTWUERMUL'HPUER CKT SUMMER MULT! PLIER CKT HJB RACT R DETECTOR I VELOCITYvumPueR cm DETECTOR 2 W we m v m 5 MULTlPUERl SUBTRAGDR BOM ROLLABILITYPREDICTION SYSTEM BACKGROUND OF THE INVENTION This invention relates torailway classification yards and more particularly to an improvedautomatic control system therefor.

One crucial calculation in the successful operation of a railroad humpyard is the ability to predict accurately the rolling behavior of a caron the bowl track on the basis of upper yard measurements. If the car isa harder roller than predicated, then the car will stop short ofcouplingto cars on the bowl track. Conversely if the the path of the caron its way to the bowl track are used to provide the car with the propervelocity.

It is known that a cars rollability changes during the course of itstravel and therefore a single rollability measurement does not alwaysprovide the proper answer for controlling the cars velocity.

OBJECTS AND-SUMMARY OF THE INVENTION An object of this invention is theprovision of a system for increasing the accuracy of the prediction ofthe cars rollability on a bowl track.

Another-object of this invention is the provision of a novel carretarder control system.

Yet another object of this invention is the provision of a novel anduseful car control system.

The foregoing and other objects of the invention are achieved by makingseveral measurements of the cars rolling behavior in the course of itstransition through the upper yard from which a fairly accurateprediction of the cars rolling behavior on the bowl track can becalculated. With this data, and from a knowledge of the distance the carhas .to roll, it is a simple matter to calculate the velocity requiredfor the car to reach its train. From a knowledge of the velocityrequired, one can measure the velocity of the car passing through thetangent point retarder, which is the last retarder just before the caris upon the bowl track. The retarder is energized to bring the carsvelocity down to the calculated value.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will best be understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of anembodiment of this invention.

FIG. 2 is a block schematic drawing of a rollability predicting circuitwhich may be employed in this invention.

FIG. 3 is a block schematic diagram of a bowl rollability predictingcircuit.

FIG. 4 is a block schematic diagram of an arrangement for controllingthe last retarder before the bowl track in accordance with thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS the From Newtons second law ofmotion of relationship between the car velocity and its rollability canbeexpressed by the differential equation:

where r dV/dt time rate of change of cars velocity (ft/sec?) ft. ofvertical drop if gmle or ft. of horizontal run g gravity constant,==32.l 6 ft/sec) R rollability A car traveling from the hump to the bowltrack will normally travel over a rollability measurement station, as aresult of which, as indicated previously the retarders are controlled todetermine the cars bowl track velocity. I

Referring now to FIG. 1, there is shown schematically a track section10in a railway classification yard and along the upper track sectionthere is a master retarder 12, followed by a group retarder 14, followedby .a tangent point'retarder 16, which is positioned just before thebowl track 18. In accordance with this invention, velocity is measuredat more than one point along the upper track. This occurs for example bydetermining the velocity with velocity detectors. A velocity'detector 20measures the velocity of a car as it comes out of the master retarder12. A second velocity detector 22 measures the velocity of the car as itenters the group retarder 14. From the difference in velocities measuredbetween these two detectors, one can compute, using the formula (1) arollability for the car which is designated as R1. This computation isprovided by an R1 computer, 24. 1 I

The velocity of the car as it leaves the group retarder v is measured bya velocity detector 26. The velocity of the car a distance downstreamfrom the exit from the group retarder is again measured by a fourthvelocity detector 28. Thedifference in velocities between the detectors26 and 28 are entered into an R2 computer, 30, which provides a secondrollability quantity designated as R2.

The rollability is again measured by using a velocity detector 32 tomeasure the velocity of the'car as it passes a given point on the track.The velocity of the car just before it enters the tangent point retarder16 is measured by a velocity detector 34. The difference between thesetwo velocities is entered into an R3 computer to produce a quantity R3.

The three (or more if desired) rollabilitymeasurements R1, R2 and R3 areentered into an R Bowl Computer 36. This measures R Bowl and applies itto a V Computer (retarder velocity) 38. This V Computer produces at itsoutput the velocity required for the car when it leaves the tangentpoint retarder. A suitable speed detector 42, such as a radar detector,measures control 44. Another input to the retarder control is the.

calculated Vs from the computer 38. The retarder control compares thesevelocities and controls the retarder to slow down the car until equalityis established at which point-the car may be released with the propervelocity.

From equation (1), the term R can be expressed in terms of two velocitymeasurements and the other quantities as:

' KiZKfi M where V measured car "velocity at point No. l (ft/sec) V,measured car velocity at a point No. 2, further down the track (ft/sec)d linear distance along the track between points No. l and No. 2 (ft.)estimated value of the average track grade between points No.1 and 2.(ft. of verticaldrop/ft.

of horizontal run between points 1 and 2). lg;- gravity constant (=32. l6 ft/s'ec) R rollability (lbs. per ton) FIG. Zshows a schematic diagramillustrative of an R1, or R2 or R3 computer. It is an analog computerderived from the equation (2).

The outputs of the first two velocity detectors 20, 22 for example areapplied to a summer 50, and to a subtractor 52 respectively providing V,V and V V outputs. These are applied to a multiplier 54. Its output,which is V} V, is applied across a potentiometer 56, the slider of whichis set to provide as output,

where the function f (R R,,R is unknown and to bedetermined by a curvefitting process.

From the mathematical theory associated with functions, it is known thatif f(R R R is well behaved,

then it can be approximated by a power series expansion in the variableR R and R The degree of accuracy to the approximation depends on thehighest order terms. The greater the number of terms in the expansionthe more accurate the approximation.

The simplest power series approximation to the unknown function flR R Ris to assume that it is linear, i;e.,

FIG. 3 is a schematic drawing of how equation (3) may be implemented sothat the term R can be automatically derived from the quantities. Theconstants a, through a are respectively derived (in a mariner to beshown later herein) by using the respective potentiometers 64, 66, 68,and 70, which are connected across potential sources respectively 72,74, 76 and 78. a is multiplied with R by a multiplier circuit 80. a, ismultiplied with R, by a multiplier circuit 82. A multiplier circuit 84multiplies a and R The outputs of the three multiplier circuits togetherwith a, are applied to a summing circuit 86. Its output is R Now inorder to determine the coefficients a through a a large number of cars,say 100 is run through the yard and for each car one measures thequantities R R, and R,. In addition one takes a velocity measurement tocalculate R This last measurement is taken in the same manner as theprevious rollability measurements by measuring the velocity of a car asit leaves the tangent point'retarder and also at a predeterminedlocation downstream from this and using equation 1. a

One now has a large collection of data consisting of. R R, and R and Rforeach car. One then uses a least square error fit technique to findthose coefficients a a a and a in equation (3) that minimize the sum ofthe square errors, that is, if there are any cause for which theexperimental data has been taken, one solves for the coefficients thatminimize the quantity all)? There are several computer programsavailable commercially which can solve this problem and find the bowlThe desired coupling speed is normally a constant. From a knowledge ofthe length of track and the number of cars already sent to form a traind is easily determined and can be automatically totaled.

FIG.- 4 shows an analog computer for calculating quantity V,, which isthe output velocity desiredfrom the tangent point retarder. The productR g is determined by a multiplier having as one input the constant 3,derived from a potentiometer 92 across a v potential source 94. Theother input is derived from a potentiometer 96 across which is appliedthe previously calculated quantity R The setting of the potentiometerprovides an output bowl .290

The output of the multiplier is applied to a subtractor 98, having asits other input the constant term 0 g. This is derived from apotentiometer 100 connected across a derived by establishing an analogquantity V by means of a potentiometer 108 connected across a potentialsource 110. The output of the potentiometer is connected to a squaringcircuit 112. This provides the quantity V The output of the summingcircuit 106 is connected to a square root circuit 114 whose output isthe term V,. 'As previously pointed out in connection with FIG. 1, V, iscompared with the actual velocity measured for the car as it is passingthrough the tangent point retarder which is instructed by any quantityto retard the car until V, and the actual measured velocity are thesame.

The circuits shown herein, being comprised of mu]- tiplier andsubtraction circuits, summers, squaring circuits and square rootcircuits, are all Well known operational amplifier circuits which arecommercially purchasable. Velocity, detectors also known as speeddetectors are well known in the art as is the radar speed measuringsystem.

Accordingly, there has been described and shown herein a novel anduseful arrangement for providing a substantially accurate measurement ofthe rollability of a car from which one can determine the properentrance velocity of a car upon the bowl track.

What is claimed is: I 1. In a railway classification yard of the typehaving a hump over which a track extends down to a bowl track section,and there is a master retarder at the hump track section, a tangentpoint retarder at the commencement of the bowl track section, and atleast one group retarder positioned along the track section between themaster retarder and the tangent point retarder, the improvementcomprising:

means for measuring a car rollability along several sections of trackbetween the master retarder and the tangent point retarder, computermeans to which the rollability measurements taken along said severalsections of track are applied for solving the equation,

where R is car bowl rollability, R R R,, are the rollability measurementmade at each of said several sections of track, a, a a a,, areempirically predetermined rollability coefficients for each tracksections along which a rollability measurement is made,

means for determining a required velocity from the derived bowlrollability for said car, I

means for measuring the velocity of said car within said tangent pointretarder, and

means for controlling said tangent point retarder responsive to saidmeasured velocity and said required velocity to provide said car withsaid required velocity as it leaves said tangent point re- 2. l i ii'fiilway classification yard as recited in claim 1 wherein said meansfor determining a required velocity from the derived bowl rollabilitytowards said car comprises a computer means for solving the equationmeans for measuring the car rollability between the master retarder andthe group retarder, the second-and third means for respectivelymeasuring the car rollability along spaced distances between said groupretarder and said tangent point retarder.

4. In a railway distribution yard having a hump and a track extendingthereover down to a bowl track, and including a master retarder at saidhump, and a tangent point retarder at the commencement of said bowltrack, a method of establishing a proper coupling velocity for a carentering said bowl track comprising:

measuring the rollability of a car at a plurality of locations as saidcar moves from said hump down toward said bowl track, multiplying eachrollability measurementby a rollability coefficient previouslydetermined for each track section along which a rollability measurementis made, adding the results of all said multiplications to obtain thebowl rollability, deriving from said bowl rollability a proper couplingvelocity for said car' to enter upon said bowl track, measuring thevelocity of said car within said tangent point retarder, comparing saidmeasured velocity with said proper coupling velocity, and controllingsaid tangent point retarder to retard the velocity of said car until itsmeasured and computed velocity are the same.

1. In a railway classification yard of the type having a hump over whicha track extends down to a bowl track section, and there is a masterretarder at the hump track section, a tangent point retarder at thecommencement of the bowl track section, and at least one group retarderpositioned along the track section between the master retarder and thetangent point retarder, the improvement comprising: means for measuringa car rollability along several sections of track between the masterretarder and the tangent point retarder, computer means to which therollability measUrements taken along said several sections of track areapplied for solving the equation, Rbowl ao+a1.R1+a2.R2+ . . . an.Rn,where Rbowl is car bowl rollability, R1, R2 . . . Rn are the rollabilitymeasurement made at each of said several sections of track, ao, a1, a2 .. . an are empirically predetermined rollability coefficients for eachtrack sections along which a rollability measurement is made, means fordetermining a required velocity from the derived bowl rollability forsaid car, means for measuring the velocity of said car within saidtangent point retarder, and means for controlling said tangent pointretarder responsive to said measured velocity and said required velocityto provide said car with said required velocity as it leaves saidtangent point retarder.
 2. In a railway classification yard as recitedin claim 1 wherein said means for determining a required velocity fromthe derived bowl rollability towards said car comprises a computer meansfor solving the equation where Vr is the required velocity, Vc is thedesired coupling speed, g is the gravity constant, theta is theestimated value of the average track grade, dr is the distance betweenthe output side of the tangent retarder and the coupling point of thecar.
 3. In a railway classification yard as recited in claim 1 whereinsaid means for measuring a car rollability along several sections oftrack between the master retarder and the tangent point retarder includea first means for measuring the car rollability between the masterretarder and the group retarder, the second and third means forrespectively measuring the car rollability along spaced distancesbetween said group retarder and said tangent point retarder.
 4. In arailway distribution yard having a hump and a track extending thereoverdown to a bowl track, and including a master retarder at said hump, anda tangent point retarder at the commencement of said bowl track, amethod of establishing a proper coupling velocity for a car enteringsaid bowl track comprising: measuring the rollability of a car at aplurality of locations as said car moves from said hump down toward saidbowl track, multiplying each rollability measurement by a rollabilitycoefficient previously determined for each track section along which arollability measurement is made, adding the results of all saidmultiplications to obtain the bowl rollability, deriving from said bowlrollability a proper coupling velocity for said car to enter upon saidbowl track, measuring the velocity of said car within said tangent pointretarder, comparing said measured velocity with said proper couplingvelocity, and controlling said tangent point retarder to retard thevelocity of said car until its measured and computed velocity are thesame.